1. Field of the Invention
The present invention relates to a wear resistant alloy for use as a material of a sliding member and also to a sliding member made of such an alloy, as well as a method of producing such a sliding member. More particularly, the present invention is concerned with a wear resistant alloy suitable for use as the material of various sliding parts or members which are used under severe sliding conditions in automobiles, ships, aircrafts and usual industrial machines, such as bushes and washers used in floating bearings of turbochargers and thrust bearings, and also to such sliding part or member, as well as a method of producing such sliding part or member.
2. Description of the Related Art
Hitherto, alloys of lead bronze alloy system (JIS H5115) or free cutting brass alloy system (JIS H3250) have been used as materials of bushes and washers of the type described above.
In recent years, sliding parts or members of the kind described must endure severer conditions of use due to, for example, increase in the speed and operating temperature of engines. As a result, alloys of a lead bronze alloy system are required to have greater resistance to decayed oils, while alloys of a free cutting brass alloy system cannot well meet the demands for resistance both to seizure and wear.
In particular, a floating bearing of a turbocharger and a thrust bearing mounted on an internal combustion engine are required to operate at higher temperatures due to increase in the rate of heat transmission from the turbine.
When an alloy of a lead bronze alloy system is used as a material of such a bearing, sulfur content of the lubricant oil reacts with copper in the bearing alloy so as to form copper sulfide. This leads to growth of a blackening layer composed mainly of copper sulfide on the bearing surface, resulting in wear and exfoliation of the surface layer of the bearing during the operation.
The alloy of free cutting brass alloy system is free from the problem of growth of blackening layer but tends to cause seizure during operation under a boundary lubricating condition, partly because of small content of lead which exhibits self-lubricative properties.